JPH0311931Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] This invention is a frequency sharing type antenna.
Even when elements with different operating frequencies are placed close together,
The present invention relates to an antenna device that functions effectively.

[Prior art]

An example of a conventional device is shown in FIG. In Fig. 1, 1 is a dipole antenna for band A, 2 is a dipole antenna for band B,
Reference numeral 3 indicates a reflector, where band B is a higher frequency band than band A.

Further, the dipole antenna 1 for band A and the dipole antenna 2 for band B are located at a distance of about 1/4 wavelength of the center frequency of each band from the reflection plate 3.

Further, it is assumed that the dipole antenna 2 for band B is sufficiently far away from the dipole antenna 1 for band A so that mutual coupling can be almost ignored.

Next, the operation will be explained.

The electromagnetic waves radiated from the band A dipole antenna 1 are bidirectional with coverage in the front and rear directions, and the electromagnetic waves radiated backward are radiated forward due to the electromagnetic effect of the reflector 3. Combined with electromagnetic waves in space.

Next, the electromagnetic waves radiated from the dipole antenna 2 for band B are also bidirectional, and the electromagnetic waves radiated backward are radiated forward due to the electromagnetic effect of the reflector 3, similar to band A. Combined with electromagnetic waves in space.

However, as shown in FIG. 2, when the conventional antenna device is used in a close area, the band B dipole antenna 2 has the disadvantage that the mutual coupling with the band A dipole antenna 1 becomes strong. As a way to solve this problem, as shown in Figure 3, from the band B dipole antenna 2 to the reflector 3 direction, 1/4 of the band B center frequency is
It is effective to provide a reflector 4 for band B at a distance of the wavelength and place it at a distance near the dipole antenna for band A, but in this case, the leakage component from the reflector 4 for band B is 3, and the distance between the band B reflector 4 and the reflector plate 3 is the band A
Because it is determined by the wavelength used by the antenna, it may interfere with the main radiation component and cause significant distortion in the antenna pattern.

[Summary of the idea]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and by attaching a resonant absorber 5 that has a remarkable power attenuation effect only in band B to the reflector plate 3, it can be used for band A. It is an object of the present invention to provide a frequency-sharing antenna device that can exhibit the original electric performance of a band B antenna without deteriorating the element performance of a dipole antenna.

[Example of idea]

Hereinafter, embodiments of this invention will be described with reference to the drawings. In FIG. 4, 5 is a band B resonance type absorber.

In the configuration shown in FIG. 4, most of the electromagnetic waves radiated backward from the band B dipole antenna 2 are spatially combined with the components radiated forward due to the electric imaging effect of the band B reflector 4. , the leakage component goes to the reflection plate 3, but is absorbed here by the band B resonant absorber 5, so that no interference with the main radiation component occurs.

Next, the electromagnetic waves radiated backward from the band A dipole antenna 1 are spatially combined with the components radiated forward due to the electromagnetic effect of the reflector 3. At this time, since the resonant absorber 5 for band B is not effective for band A, the combining effect can be obtained without any problem.

Although one antenna element was used in each of the above embodiments, a plurality of antenna elements can be arranged and used as an array antenna. In addition, the antenna element is not limited to dipole antennas, but can be applied as long as it has bidirectional properties, and the absorber does not need to be of the resonant type, and it can be used to reduce the amount of attenuation that is significant in one of both the A and B bands. Any absorbent body that exhibits the following may be used.

[Effect of idea]

As described above, according to this invention, the detection distance can be extended because band A gain does not decrease, and band B has the effect of obtaining the desired performance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional frequency sharing type antenna device, FIGS. 2 and 3 are diagrams showing a case where each element in FIG. 1 is placed close to each other, and FIG. 4 is a diagram showing a frequency sharing type antenna device according to an embodiment of the present invention. FIG. 2 is a diagram showing a type antenna device. In the figure, 1 is a band A dipole antenna, 2
is a band B dipole antenna, 3 is a reflector,
4 is a B-band reflector, and 5 is a B-band resonant radio wave absorber. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] In a frequency sharing type antenna device in which first and second antenna elements each having a different usage band are arranged on the same aperture surface on a reflector, a reflector for the first band is provided behind the first antenna element. An antenna device further comprising: a radio wave absorber having a power attenuation effect in the operating frequency band of the first antenna element is provided on the reflector.